Podcaster: Morgan Rehnberg
Title: Monthly News Roundup – Glowing in the Dark
Link : http://cosmicchatter.org
Dark matter: http://astronomy.com/news/2013/09/texas-astronomers-unravel-20-year-mystery-about-dark-matter
Mars methane: http://www.nytimes.com/2013/09/20/science/space/mars-rover-comes-up-empty-in-search-for-methane.html?pagewanted=all
Black holes: http://www.space.com/22736-monster-black-holes-nasa-discovery.html
Dark energy: http://www.fnal.gov/pub/presspass/press_releases/2013/DES-20130903.html
Voyager 1: http://www.slate.com/blogs/bad_astronomy/2013/09/13/voyager_1_space_probe_is_in_now_in_interstellar_space.html
Description: On this episode of the Monthly News Roundup, we launch a spacecraft to the Moon and another one enters interstellar space. New studies probe the dual mysteries of dark energy and dark matter. A search for black holes comes up positive and one for methane does not.
Bio: Morgan Rehnberg is a graduate student in astrophysics and planetary science at the University of Colorado – Boulder. When not studying the rings of Saturn, he develops software to help search for asteroids that might hit the Earth. He blogs and podcasts about astronomy and space science at http://cosmicchatter.org.
Today’s sponsor: This episode of “365 Days of Astronomy” is sponsored by — no one. We still need sponsors for many days in 2013, so please consider sponsoring a day or two. Just click on the “Donate” button on the lower left side of this webpage, or contact us at firstname.lastname@example.org.
You’re listening to the 365 Days of Astronomy Podcast for September 29th, 2013. I’m Morgan Rehnberg, here with Vivienne Baldassare, and this is the Monthly News Roundup. This episode was produced by Cosmic Chatter in Boulder, Colorado. This episode contains information about the LADEE spacecraft, which includes components built by my employer, the Laboratory for Atmospheric and Space Physics at the University of Colorado.
Man last walked on the Moon more than forty years ago, but we’re finally on track to follow up on one of the Apollo astronauts’ most surprising observations. While never captured on film, several moonwalkers sketched the lunar sky as having a faint glow. In the decades since the last Apollo mission, two theories have emerged. Some scientists propose that the glow is simply dust floating above the surface and catching the sunlight. Others suggest that fluorescent sodium might be responsible.
To answer this question and several others, this month NASA launched the LADEE spacecraft to the Moon. In the next three months, it will search for evidence to validate one of these two theories.
In addition to this, LADEE aims to establish baseline measurements of the lunar atmosphere before further human exploration disturbs it. As the pace of the Moon’s exploration picks up in the coming decades, we will undoubtedly affect its environment. To help measure these changes, LADEE will make a detailed study of the dust and molecular composition of the lunar atmosphere today.
The mission is also a testbed for some exciting new technology. LADEE is the first spacecraft to be built using a new, modular design. By reusing parts from mission to mission, NASA hopes to cut down on some of the high development costs that all space missions involve. This isn’t the first time components have been reused: the 2007 Phoenix Mars Lander reused several parts first developed several years earlier for the Spirit and Opportunity rovers.
LADEE will also be the first mission equipped with a laser communication system. NASA hopes this demonstration system will prove that laser communication is ready for deployment on many future spacecraft. Laser communications offer distinct benefits over the current radio systems, including reduced power consumption and increased data transfer rates.
If all goes well during her 100-day mission, LADEE should advance both our understanding of the Moon and the technology we use to explore it. We’ll be keeping an eye on her in the upcoming months.
The majority of matter in our universe is so-called “dark matter”. It is known as this because it doesn’t emit or absorb light. Though we cannot see it, we infer its presence by observing how it gravitationally interacts with matter we can see. Dark matter actually makes up the vast majority of the matter in our universe. This makes knowledge of dark matter essential for understanding the formation and evolution of galaxies, which contain between 10 and 1000 times as much dark matter as normal matter. Small galaxies in particular contain much more dark matter than normal matter.
Astronomers have long disagreed about how dark matter is distributed throughout small galaxies. While some think it is distributed evenly across the galaxy, others believe the amount of dark matter decreases as you move outwards from the center.
Astronomers at the University of Texas at Austin set out to solve this problem by looking at small galaxies orbiting the Milky Way. They used a supercomputer to test which models best described the dark matter distributions of these objects, and found that while the dark matter distributions varied for different galaxies, on average, the dark matter was denser in the center. They attribute these variations to galaxies developing in slightly different ways.
Is it possible to detect dark matter observationally? Yes. While dark matter doesn’t interact electromagnetically with light, it can still affect it through the force of gravity. If you bunch up a lot of mass, the gravity can become strong enough to noticeably bend light. This effect is called gravitational lensing. However, this lensing is only observed around large objects like galaxy clusters. For now, computer models may remain our best tool to understand this important phenomenon.
For decades, the search for life has been among the most attractive reasons to explore Mars. Over the years, a number of pieces of evidence have suggested that life could survive on the red planet. In the 1970s, a test for organic material aboard one of NASA’s Viking landers came up positive. More recently, Spirit, Opportunity, and Curiosity have found evidence indicating that liquid water may have been present on the Martian surface at some point in the past.
But for every supporting discovery, it seems as if another crops up to refute it. The second Viking lander never identified any organic materials. Global maps of the surface indicate that no water survives there today. And this month, Curiosity sadly supplied yet another blow to our hopes of finding life on Mars.
This time the culprit is methane. The simple gas is produced by all sorts of life here on Earth, from microbes to cows to humans. On Mars, Curiosity detects not even a trace. Of course, far from all life on Earth produces methane, so this doesn’t completely rule out martians. But methane is a common sign of microbes, the only sort of life that most scientists believe we have a chance of finding.
This discovery only casts doubt on microbes alive today. Billions of years ago, we believe Mars was warm and wet – perfect conditions to foster life. Microorganisms back then could have produced tons of methane, but we wouldn’t know it today. That’s because Mars dried up about three and a half billion years ago, and it only takes light from the Sun a few hundred years to break up the gas.
NASA’s NuSTAR telescope has discovered 10 black holes in distant galaxies. NuSTAR is an x-ray telescope orbiting Earth, and it was designed in part to find black holes, or regions of space so dense that not even light can escape their gravitational pull. Material surrounding a black hole interacts and heats up to extremely high temperatures and emits x-rays. These 10 black holes were found by accident – the galaxies they live in happened to be in images taken of other galaxies. NuSTAR is expected to find hundreds more black holes over its lifetime.
Observing x-rays is tricky. They are far smaller and higher energy than visible light waves and thus we can’t use the same technology to observe them. Normal telescopes bounce light off mirrors and into detectors. However, if you were to shine a beam of x-rays at a mirror, more would be absorbed than reflected. Instead, engineers build mirrors made of gold foil at steep angles. The x-rays graze against the surface of the mirror and are redirected into the detector.
By searching for black holes in galaxies that span a wide range in age, we hope to learn about the activity of black holes in nearby and distant galaxies. In addition, how many galaxies contain black holes in their centers is related to how these supermassive black holes formed in the first place, something astronomers are still unsure about. NuSTAR’s observations will help us learn about the population of black holes in our universe, and how they and their host galaxies change with time.
In addition to hunting black holes, NuSTAR is well-suited to observe other astronomical objects that emit very high-energy light, such as supernovae, and jets that expel material from the centers of galaxies.
August 31st marked the start of the Dark Energy Survey, a study designed to help us better understand why the universe is expanding faster. We attribute this accelerating expansion to “dark energy”, a force which works against gravity to push objects apart. Over the next few years the Dark Energy Survey will observe hundreds of millions of galaxies, as well as supernovae and galaxy clusters, detecting objects up to eight billion years light-years away. Scientists plan to study these objects at different points in time to learn about the history of the Universe’s expansion.
Although we can’t directly observe dark energy, we can learn a lot about it by observing these distant galaxies. Since the formation of a galaxy cluster depends on how well gravity can overcome the dark energy pushing galaxies apart, the number of galaxy clusters at any given time can help us learn about how much of an influence dark energy had at that point in cosmic history. By observing more than 100,000 galaxy clusters over the course of 8 billion years, the Dark Energy Survey will tell us about the evolution of dark energy’s effect on our universe.
Supernovae observations will help us learn about how fast the universe’s expansion is speeding up. Since the observed supernovae all have roughly the same intrinsic brightness, we can use the amount they are dimmed by to figure out how far away they are. Using information we gain from these supernovae observations, we can determine how quickly the universe has grown over time.
Finally this month, we found out that one of mankind’s greatest adventures has finally taken its next step. The Voyager 1 spacecraft, launched September 5th, 1977, has officially entered interstellar space, the region between stars. This was a moment long anticipated by the famous astronomer Carl Sagan, who spearheaded the effort to include a “golden record” on board both Voyager ships. The record contains a selection of images, sounds, and ideas representative of all the Earth’s cultures. Inscribed next to the record is a map pointing to Earth and directions on how to use the record.
The Voyager mission represents the pinnacle of NASA’s ambition in unmanned exploration. Together the twin ships explored Jupiter, Saturn, Uranus, and Neptune before heading out of the solar system. Voyager 1 is now the first manmade object to venture into interstellar space, and Voyager 2 remains the only craft to ever study Uranus and Neptune.
I have to admit a sense of jealousy regarding the Voyager science teams. They had an opportunity not unlike that which faced Galileo at the dawn of modern astronomy. They were the first to explore vast tracts of our solar system. The Voyagers revealed new rings, new moons, and remarkable new phenomena which still baffle us today.
Reading the work of these scientists, it’s clear that they were not immune from being in awe of what they were doing. Like modern-day Magellans, everywhere they looked revealed some incredible new discovery. And as Magellan was followed by a fleet of more specific expeditions, today we continue to follow up on the discoveries of the Voyager program. They drew the outlines of the solar system – it’s time for us to fill in the details.
Thanks for listening to this episode of the 365 Days of Astronomy. For more astronomy news and commentary, visit www.cosmicchatter.org or follow @cosmic_chatter on Twitter. As always, you can contact us with your comments and corrections at email@example.com. See you in October
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365 Days of Astronomy
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